Reactivity in the human retinal microvasculature measured during acute gas breathing provocations

Abstract

Although changes in vessel diameter following gas perturbation have been documented in retinal arterioles and venules, these responses have yet to be quantified in the smallest vessels of the human retina. Here, using in vivo adaptive optics, we imaged 3-25 μm diameter vessels of the human inner retinal circulation and monitored the effects of altered gas-breathing conditions. During isocapnic hyperoxia, definite constrictions were seen in 51% of vessel segments (mean ± SD for pre-capillary arterioles -9.5 ± 3.0%; capillaries -11.8 ± 3.3%; post-capillary venules -6.3 ± 2.8%); these are comparable with responses previously reported in larger vessels. During isoxic hypercapnia, definite dilati..